1. Technical Field
The present disclosure relates to detecting the presence of persons in a field of view. The present disclosure applies, for example, to the protection of confidential information presented on a display screen of a fixed or mobile electronic apparatus, such as a personal computer, a mobile telephone or a PDA (Personal Digital Assistant).
2. Description of the Related Art
The use of such an apparatus particularly in a public place may expose confidential information displayed on the screen to non-authorized persons. To try to solve this problem, so-called privacy filters in the form of a film arranged on the screen to reduce the width of the field of view of the screen, centered on a perpendicular axis and centered on the screen have already been proposed. Such a filter, which is for example described in the document WO 2007/118122, enables people in the vicinity of this axis to view the information displayed, this information not being generally visible to persons located outside this axis. Such a filter does not therefore prevent a person located behind the user in the vicinity of this axis from viewing the information displayed. In addition, such a filter affects the colors and the brightness of the images displayed by the screen. To offset this negative effect, the brightness of the screen can be forced, but this increases the current consumption of the screen, which is not desirable in the case of battery-powered apparatuses.
Document WO 2006/023384 in particular, also proposes an electronic filter which can be enabled or disabled according to the needs of the user. When enabled, this filter behaves substantially in the same way as the passive film arranged on the screen described above. However, this solution may use resources of the apparatus to change the images displayed so as to limit the field of view of these images. This solution also requires the user to manually enable or disable the electronic filter. The user may therefore forget to enable the filter when controlling the display of confidential information on the screen of the apparatus, or may not notice that a person has approached the screen and may have access to the information displayed. Some users thus prefer to leave the filter on at all times to avoid forgetting to enable it. In this case, this filter thus has substantially the same disadvantages as the passive filter described above in terms of the brightness and overconsumption of the screen.
The use of such an electronic filter also has the disadvantage of making the apparatus more complex to use. This disadvantage can be mitigated by providing an additional command button on the apparatus. However, adding such a button may involve integration problems, particularly when the apparatus is small, as is the case of mobile telephones, and induces an extra manufacturing cost.
Furthermore, such filters, whether passive or electronically enableable, do not protect confidential data introduced by means of a keyboard of the apparatus. Indeed, an ill-intentioned person may observe the movements of the user's fingers for example while the latter enters a confidential code, and thus have access to such a code without the user knowing.